The invention relates to a method for selective laser sintering in which a workpiece is produced layer by layer by irradiating a powder bed formed of the material of the workpiece by at least one linear application of energy of a laser beam. The invention also relates to a system for selective laser sintering with a process chamber, in which a support for a workpiece to be produced and a powder distributor for creating a powder bed on the support are provided.
A method of the type specified at the beginning is known for example from DE 10 2006 059 851 B4. In the case of the method for selective laser sintering that is described, a workpiece is produced by the individual layers of the powder bed being melted by a plurality of linear applications of energy of a laser beam. The linear applications of energy are in this case in straight lines and respectively extend only over individual portions of the surface area to be produced of a layer that cover a segment of the overall surface area. In this case, the individual applications of energy are combined with one another, with the stipulation that only one linear application of energy respectively takes place alternately in each sub-portion, so that this individual portion can in each case cool down before the next application of energy. The aim is to obtain a lower-stress microstructure of the component produced.
The linear applications of energy of neighboring sub-portions of the surface area are preferably aligned at right angles to one another. Here it is unavoidable that the linear applications of energy respectively end at the contour-forming ends of the cross-sectional area to be produced in the powder bed. Here the process causes a certain surface roughness to be created in the contour, dictated by the width of the melt bath of the selective powder melting. It follows from this that the achievable surface quality of the selective laser sintering concerned is limited by the process. If it is intended to produce a better surface quality with given parameters for the selective laser sintering, this can only be achieved by reworking of the surfaces.
A system for selective laser sintering is known from DE 10 2007 036 370 B3. This system has a support for a workpiece in a chamber. This support is distinguished in particular by the fact that it is provided with a recess, so that a prefabricated workpiece can be inserted there. With the part protruding from this recess, the workpiece can then be subjected to a treatment by selective laser sintering in the system. For this purpose, the powder from which the workpiece is intended to be produced is applied to the support. A powder distributor, which includes a metering device and a doctor blade, is used, these devices allowing a planar surface of the powder bed to be created. The laser inscribes as it were the cross section of the workpiece to be produced in the surface in the layer concerned, so that the workpiece is completed layer by layer.
According to EP 1 419 836 A1, it is known that the laser can be guided crosswise in the successively produced layers to even out the structure that is created by the laser sintering. In order to improve the structure in the peripheral region of the component created, it may be provided according to U.S. Pat. No. 5,155,324 that the contour is followed by the laser in the respectively produced layer of the component. Specifically for annular cross sections of the component that are created, it may be provided according to DE 101 12 591 A1 that the laser is guided spirally, for example from the outer contour to the inner contour. According to DE 10 2006 059 851 B4, it is also proposed that, to improve the result, the cross-sectional area to be created of a component may be notionally divided up into different regions, parts of the cross section being produced in different regions in continuous alternation, so that at the end the complete cross section is melted.
DE 102 35 434 A1 presents a machine for generative production processes in which the building platform on which the powder is applied layer by layer is movably arranged. This platform can in particular be rotated about an axis of rotation and thereby raised or lowered according to the layer produced.
DE 10 2008 056 336 A1 also describes that generative production processes can also be used, inter alia, as methods for repairing turbine blades.